Ulster stretched their unbeaten start to the RaboDirect PRO12 season with a narrow 27-25 victory over basement side Zebre on Sunday.

The Irish province extended their lead at the top of the table thanks largely to a converted penalty try five minutes. The match-winning score was awarded after the home scrum buckled under pressure from Ulster, and Niall O'Connor added the crucial extras to earn the win. The victory maintained Ulster's 100 per cent start to the 2012-13 campaign, while Zebre are still to even draw a match, though they had the consolation of two bonus points here.

Ulster forged ahead through an O'Connor penalty but Zebre scrum-half Tito Tebaldi touched down after 10 minutes to put the Italians in front. Two more O'Connor penalties restored Ulster's advantage, but Daniel Halangahu's penalty kick reduced the deficit to one point at half-time.

Halangahu then crossed for a try to put Zebre 13-9 ahead, and although O'Connor kept Ulster in touch the first of two tries for South African Dries van Schalkwyk extended the hosts' lead to 18-12.

Ulster reacted strongly and Paddy Wallace touched down on the right-hand side after good work from Jared Payne, and although O'Connor failed to convert he did strike another penalty to put the visitors two points ahead. But Zebre did not buckle and Van Schalkwyk claimed his second try as he charged off the back of a retreating Zebre scrum, with Halangahu's extras giving them a 25-20 lead.

At that stage they looked good for victory, but the concession of the penalty try ultimately proved very costly.